ABSTRACT: Loss of cardiomyocytes (CMs) following injury can lead to myocardial dysfunction, heart failure (HF) and ultimately death. The limited regenerative ability of the adult human heart after injury, however, poses a significant obstacle to restore cardiac function effectively. While mammalian hearts, including those of mice and humans, do have the potential to regenerate, this capacity is restricted to a narrow window during early stages of life. The molecular mechanisms governing the regenerative capacity of mammalian hearts remain incompletely understood. Exploring a comparative transcriptome analysis in regenerative neonatal vs. non-regenerative adult mouse CMs, we identified N-Cadherin, a member of Ca2+-dependent cell adhesion protein cadherin superfamily, as a potential novel regulator of CM proliferation/renewal. The primary objectives of this study were to elucidate the molecular mechanisms through which N-Cadherin regulates cardiomyocyte proliferation and regeneration, and to determine the therapeutic potential to promote CM renewal and restore cardiac function following injury by targeting N-Cadherin. Cardiac N-Cadherin expression exhibits a strong positive correlation with that of cell cycle- and proliferation-related genes. Its expression levels show an age-dependent reduction, with a 75% decrease of N-Cadherin in adult, compared to P1 neonatal, CMs. N-Cadherin expression is upregulated in the neonatal mouse heart in response to apical resection, especially in the peri-injury region, coinciding with increased CM mitotic activities in the neonatal heart. Knocking down N-Cadherin reduced, whereas overexpression of N-Cadherin increased, the proliferation activity of neonatal mouse CMs and human induced pluripotent stem cell-derived CMs. Mechanistically, increased N-Cadherin potentiates CM renewal through direct binding with and stabilization of a pro-mitotic transcription regulator β-Catenin, leading to increased CMs proliferative activity. Deletion of β-Catenin-binding domain on N-Cadherin abrogated its pro-regenerative activity. Importantly, targeted depletion of N-Cadherin in CMs resulted in incomplete cardiac repair/regeneration and excessive fibrotic scar formation in neonatal mouse hearts following injury. Cardiac-specific overexpression of N-Cadherin in adult mouse heart using adeno-associated viral vectors, by contrast, resulted in increased CM proliferation and protected against myocardial infarction-induced adverse remodeling and contractile dysfunction. Adherent junction protein N-cadherin is demonstrated to play a crucial role in maintaining CM renewal potential by post-translational stabilization of β-Catenin. Enhancing N-cadherin expression levels and downstream signaling activities in the heart, therefore, could be a powerful new approach to promote cardiac regeneration and restore myocardial function in adult human heart following injury.
